*{
    padding: 0;

}
.dingbu{
    width: 100%;
    text-align: center;
    background-color: #4caf50; 
    color:aliceblue;
    position: fixed;
    top: 0;
}
.jieshao{
    width: 100%;
    text-align: center;
    background-color: black;
    color: aliceblue;
    margin-top: 147px;

}
.dibu{
    width: 100%;
    height: 80px;
    text-align: center;
    background-color: #4caf50; 
    color:aliceblue;
    position: fixed;
    bottom: 0;
    
}
.biao{
    width: 80%;
    margin-bottom: 7%;
}